This invention relates to an improved process for preparing certain dialkyl propanediimidate dihydrohalides.
McElvain and Schroeder, JACS 71, 43 (1949), disclose the preparation of dimethyl and diethyl propanediimidate dihydrochloride by treating malononitrile and the corresponding alcohol with a large excess of hydrogen chloride using a chloroform-dioxane mixture and dioxane, respectively, as solvents. The process is disclosed to give high yields, but a reaction time of about twenty-four hours is required.
U.S. Pat. No. 4,310,740, issued on Jan. 12, 1982 to Adams, discloses an improved process for preparing a dialkyl propanediimidate dihydrohalide by reacting malononitrile, an alcohol and hydrogen halide in an alkyl acetate solvent.
Imido ester hydrohalides are well-known compounds. They are useful as chemical intermediates for other chemical compounds such as amidine hydrochlorides or as intermediates for herbicides as described in U.S. Pat. Nos. 4,287,343 and 4,229,960. Improvements in the process for preparing these imido ester hydrohalides, for example, improvement providing greater economy and ease of operation, are increasingly desirable.